A reversing cut plate-equipped boring tool is described, for example, in EP 0 750 960 A1. This boring tool has a borer body which has a shaft arranged for fastening to a corresponding chuck on one end and two plate seats on its other end. On the plate seats there are held essentially square reversing cutting or cut plates each having four cutting edges which are constructed. The cutting edges are bent slightly concave in order to smooth the bore wall definitively with a side blade, which engages the bore wall solely with a corner or a short section.
The two reversing cut plates held on the face side of the boring tool in corresponding plate seats overlap reciprocally on the tool face. With this arrangement, in particular, the sections of the cutting edges following upon the corner blades act with a shaving removing effect. The exact relations of the two reversing cut-plates are dependent on the borer diameter and, accordingly, on the extent to which the reversing cut plates overlap. Furthermore, with square reversing cut plates of a given size, more than two reversing cut plates are required if the borer radius is greater than twice the edge length of one reversing cut plate.
Boring tools with reversing cut plates are also known from WO 93/02824. This boring tool has a borer body with two face-side plate seats on which there are held rotating cut plates essentially rectangular in shape. Specifically, on the rotating cut plate there are formed two shorter concavely curved cutting edges lying opposite one another, which over an arcuately curved projecting corner blade extend into similarly concave-constructed longer flanks which do not function as a cutting edge. The reversing cut plates are thus attuned in their size to the borer diameter in such manner that the radially farther outside positioned reversing cut plate stands with its inside-lying corner blade approximately in the area of the middle of the cutting edge of the reversing cut plate arranged radially inside. Therefore, the machining is concentrated mainly in the areas near the corner of each cutting edge, whereas the middle sections are largely unburdened.
A boring tool with triangular cutting plates is known from DE 4018043 A1. With this boring tool each cutting edge is constructed either arcuately convex or with a corresponding jog. With corresponding overlapping of several cutting edges on the reversing cut plates provided on the borer face side, a blade extending in a corrugated or in zig-zag manner is produced. The radially inside-arranged cutting plate extends with its corner edge somewhat beyond the axis of rotation. The point lying furthest forward axially, however, forms approximately the middle of the cutting edge of this reversing cut plate. This point lies at a relatively great distance from the axis of rotation. This can result in problems when starting a boring operation. Furthermore, the use of the same reversing cut plates on boring tools having different diameters can lead to different amount of overlapping of the reversing cut plates. As a result of their convexly curved or convexly bent geometry, the edges of the reversing cut plates come into engagement with the work piece in ever shorter sections which can lead to non-uniform stresses on the cut plates and the boring tool.
As general rule, cutting plates are designed for the borer, i.e. for the basic tool, for which they are provided. Thus, for different tool diameters, for right-spiral tools and for the left-spiral tools different cutting plates must be provided. As will be appreciated, this presents a significant economic burden.
Furthermore, in many boring tools, the cutting plates are set in such a way that during the machining process a radial force is produced which deflects the basic tool body in a radial direction. This leads to an increase of the bore diameter, which is otherwise dependent on the length of the tool, on the turning rate of the tool, and on the material removed.